This invention relates to tuneable RF resonators and more particularly to helical coil resonators wherein tuning is achieved by dielectric loading of the inside and outside of the helical coil.
Tuneable helical resonators are very effective for use at radio frequencies of relatively high power. Such helical resonators are basically distributed parameter devices and provide extraordinary high unloaded Q's. This property leads to low loss since insertion loss, as a first order effect, is a function of the ratio of Q loaded/Q unloaded. Hence for a fixed bandwidth, the larger the Q unloaded, the lower the loss. However, it has been found that for this type of resonator, tuning becomes a problem since relatively large capacitors must be used in order to withstand the relatively large voltages.